Our initial studies among non-depressed elderly revealed that sleep and EEG variables serve well as markers for onset but not for the further progression of Alzheimer's dementia. This continuation project expands these studies to examine these and other potential diagnostic aids in medically healthy elderly with varying degrees of depression, half of whom have diagnosable early Alzheimer's dementia and half of whom have undiagnosable memory complaints. Sleep architecture, REM sleep distribution, EEG (dominant occipital frequency, diffuse slowing, and coherence measures) and circadian temperature variables will be examined for ability to distinguish depression from dementia in this population. Analyses will be performed to determine the discriminitive power of these measures to correctly classify individuals as demented vs. non-demented and/or depressed vs. non-depressed. In addition, these variables will be examined in multiple regression analyses to test our hypotheses that specific set of variables may account for variance in cognition not attributable to depression, and that a different set of sleep EEG and temperature variables may account for variance in depression.